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Are yeast capable of independent locomotion ? How do they "find" the sugar ?

Asked another way ...

When my mash is in the fermenter, and the yeast added to the top, do they stay within a horizontal plane consuming the sugar until the specific gravity causes them to drop to the next plane where the sugars are consumed, until the SG reaches a point where the yeast is no longer buoyant ? Or will the yeast attain a distribution, top to bottom, throughout the mash ?

Wikipedia provided no answers. Not that this knowledge is likely to change my protocol but I'm curious as to how the yeast can so efficiently consume virtually all the available sugar.

They mix in then drop out when the job is done.

I got this from cryptobrewology.com

All yeast will mix in with the “solution” in order to consume sugars in the wort, or must in the case of wine making. All yeast will settle to the bottom of the fermentation vessel, creating a layer of silt, or sediment, when they’re through. -

Basically what bear said.

Great question, Greggn. Not one I ever thought much of nor would I have, but after reading your question found myself wondering. Your question answered one I had that I didn't even know I had.

>All yeast will mix in with the “solution” in order to consume sugars in the wort

I'm still not clear on how yeast in position "X" eventually consumes sugar that occupies position "Y." I'll assume that the release of CO2 causes turbulence in the solution that results in random collisions between the yeast and sugar.

CO2 and convection. Yeast are exothermic when doing their deed. Ferment in a glass carboy with a flocculant yeast and you'll see the churning is quite aggressive.

> CO2 and convection.

That makes perfect sense ... thank you.

3d0g
is correct, with in all the other categories of yeast theres bottom fermenting and top fermenting yeast. as distillers we use top fermenting yeast
my old fermenter I had wound copper coils down one side of the fermenter, really good convection. The coiled copper was attached to a chest cooler with coolant running through it. So the environment in the fermenter was warm on one side cool on the other

moosemilk wrote:Great question, Greggn. Not one I ever thought much of nor would I have, but after reading your question found myself wondering. Your question answered one I had that I didn't even know I had.

Bofus . Thanks for the question and the answers it has generated . Like Moose I had not considered that . Good for someone to pose a question to kick us off our complacent asses and back into thinking mode .

Watching an active ferment in a glass carboy reminds me of lava lamps.

Does anyone stir there ferment?

Yes Butt....Butt..... Butt.....
only if I've changed the ph or something like that in the first day or so. After that I've have it just right and it's time to think about something else until it's done.

On sugarheads, I usually stir the fermenter a couple of times on the first day to keep everything in suspension.
Also stir once near the end of fermentation when the yeast isn't active enough to stir the fermenter itself.
Then I let the yeast flocculate and clear before racking at least once.
On a mash, I'll stir more often. The main thing is oxygen is good at first and bad after that.
Posting at the same time as LL

Good question
but theirs too many variable to answer in just a few sentences.
Life experiences really is the short answer. But if you think there's something to gain by stirring then do it, if not don't
just what shadylane said, what do you have to gain from it?

Deerhunter wrote:Does anyone stir there ferment?

After initial aeration my experimental washes only get opened to take SG samples for progress readings, and those are only taken for statistical data collection... Aside from that I leave them unmolested... For an established recipe I just let the wash go until fermentation stops... Stirring really isn't required as the yeast find the fermentable sugars just fine on their own...

Yeast are completely non-motile they cannot purposely cause themselves to move in any particular direction. They simply disperse and move about randomly with whatever current that happens to take them, until they flocculate and fall to the bottom.

Bottom and top fermenting yeast classification came about because some form a cap and others don't. This doesn't mean that the top fermenting yeast are all floating on top of the wort. If you ferment in a clear container you will see the yeast cloud the entire wash.

rad14701 wrote:

Deerhunter wrote:Does anyone stir there ferment?

After initial aeration my experimental washes only get opened to take SG samples for progress readings, and those are only taken for statistical data collection... Aside from that I leave them unmolested... For an established recipe I just let the wash go until fermentation stops... Stirring really isn't required as the yeast find the fermentable sugars just fine on their own...

Exactly. Yeast will run it's course without meddling.

*henh* He said "flocculate". *henh* *henh*

tp

Bagasso wrote:Bottom and top fermenting yeast classification came about because some form a cap and others don't. This doesn't mean that the top fermenting yeast are all floating on top of the wort. If you ferment in a clear container you will see the yeast cloud the entire wash.

What makes top fermenting yeasts cause the cap to rise where bottom fermenters don't?
Interesting thread!

Yeast will definitely find their way through all the sugars just fine. In fact its recommended when making beer to add the yeast to the top and NOT stir it in. Why? Because if stirred in the yeast will go ballistic straight out and explode your wash in a frenzy, with too much heating up of the wort and high probability of the krausen (yeast cap) exploding the lid off your ferment bucket.

The only time I stir is when Im fermenting fruit, punch the cap down into the liquid every couple days where it can do the most good to add flavors and fermentables. If youre fermenting AG's on the grain you could do this also, but its optional and you gotta be aware every time you open your ferment bucket youre disturbing the protective layer of CO2 and letting nasties in.

Dan P. wrote:What makes top fermenting yeasts cause the cap to rise where bottom fermenters don't?

Seems like the classification is a bit outdated. Bottom fermenters were mainly used for lagers.

What causes the cap is co2 so, what really causes the difference is the fermentation rate. Since lagers are fermented slowly they don't form co2 quickly enough to form a cap and if there was no cap they must have been all hanging out at the bottom.

Old school logic.

Bagasso wrote:

Dan P. wrote:What makes top fermenting yeasts cause the cap to rise where bottom fermenters don't?

Seems like the classification is a bit outdated. Bottom fermenters were mainly used for lagers.

What causes the cap is co2 so, what really causes the difference is the fermentation rate. Since lagers are fermented slowly they don't form co2 quickly enough to form a cap and if there was no cap they must have been all hanging out at the bottom.

Old school logic.

Ah-ha!

Deerhunter wrote:Does anyone stir there ferment?

Not excactly stirring it, but i shake it.
I always airiate a new ferment. yeast needs oxygen to reproduce.
So i give it some air from a cheap aquarium pump i bought..give it half a hour or so, then cap the jug.
The yeast should double their count roughly every three hours.
I leave it alone, so they can start to do their job on producing alcohol.
Once a day the first three or four days , i give it a good shake.
I am yet to have a ferment that fails to produce or stucks, because of stressed yeast.

Dan P. wrote:

Bagasso wrote:

Dan P. wrote:What makes top fermenting yeasts cause the cap to rise where bottom fermenters don't?

Seems like the classification is a bit outdated. Bottom fermenters were mainly used for lagers.

What causes the cap is co2 so, what really causes the difference is the fermentation rate. Since lagers are fermented slowly they don't form co2 quickly enough to form a cap and if there was no cap they must have been all hanging out at the bottom.

Old school logic.

Ah-ha!

I is also a difference between what's called top fermenting yeast and bottom fermenting yeast...lager is made with bottom fermenting yeast.
Lager is also fermenting on lower temperatures, hence the longer fermentation time.

They are different strains. Ale yeasts are Saccharomyces cerevisiae, lager yeasts are Saccharomyces pastorianus. They behave differently when fermenting sugars. Lager yeasts tend to ferment more completely, drier (higher attenuation) and take 3 weeks or so to ferment out (due to the colder temps). Ales can be mostly done in 3-5 days. Lagers also tend to produce sulpher compounds (diacetyls) but will consume their own diacetyls with a rest at 60F for a couple days after the primary fermentation is done (3 weeks at 48F or so).

Why one forms a krausen (foamy top) and the other sinks I dunno, Bagasso is prolly right. Anyone who's watched yeast work in a carboy tho can plainly see the yeast are busy throughout the whole ferment, churning and moving the wort around with lots of the activity.

Lagers are fun to make but a bit of a pain in the ass. You need a 'lagering chest' , like an old freezer with a temp controller on it, and 5 weeks or so, cranking temps from 48 (ferment) to 60 (diacetyl rest) to 32 (cold crash). Its pretty rewarding when you nail one tho, like a good Czech Pilsner style (Pilsner Urquel), crisp, clean, clear with nice Saaz hops aroma.

Ive been meaning to try a whiskey ferment with a lager yeast. One day, its on the list.

Bla bla. Sorry, site is slow today thought Id yammer on here for a bit....